December 2001 arXiv papers — page 19

I. Kuzmenko, S. Gredeskul, K. Kikoin, Y. Avishai

Spectrum of boson fields and two-point correlators are analyzed in a quantum bar system (a superlattice formed by two crossed interacting arrays of quantum wires), with short range interwire interaction. The standard bosonization procedure is shown to be valid, within the two wave approximation. The system behaves as a sliding Luttinger liquid in the vicinit

Martin Bojowald, Thomas Strobl

Constrained Hamiltonian systems fall into the realm of presymplectic geometry. We show, however, that also Poisson geometry is of use in this context. For the case that the constraints form a closed algebra, there are two natural Poisson manifolds associated to the system, forming a symplectic dual pair with respect to the original, unconstrained phase space

C. Emary, R. F. Bishop

We present a new method for finding isolated exact solutions of a class of non-adiabatic Hamiltonians of relevance to quantum optics and allied areas. Central to our approach is the use of Bogoliubov transformations of the bosonic fields in the models. We demonstrate the simplicity and efficiency of this method by applying it to the Rabi Hamiltonian.

Yoshifumi Hyakutake

Classical configurations of a M2-brane, a D2-brane and D0-branes are investigated in the background of an infinite array of M5-branes or NS5-branes. On the M2-brane, we discuss three kinds of configurations, such as a sphere, a cylinder and a torus-like one. These are stabilized by virtue of the background fluxes of M5-branes. The torus-like M2-brane configu

Giancarlo D'Ambrosio, Gino Isidori

Motivated by the new experimental information reported by the BNL--E787 Collaboration, we analyse the present impact and the future prospects opened by the measurement of $\br(K^+\toπ^+ν\barν)$. Although still affected by a large error, the BNL--E787 result favours values of $\br(K^+\to π^+ν\barν)$ substantially larger than what expected within the Standard

Shin'ichirou Yoshida, Luciano Rezzolla, Shigeyuki Karino, Yoshiharu Eriguchi

We have computed the eigenfrequencies of f-modes for a constant-rest-mass sequences of rapidly rotating relativistic inviscid stars in differential rotation. The frequencies have been calculated neglecting the metric perturbations (the relativistic Cowling approximation) and expressed as a function of the ratio between the rotational kinetic energy and the a

Romuald A. Janik, Maciej A. Nowak

We provide a compact exact representation for the distribution of the matrix elements of the Wishart-type random matrices $A^\dagger A$, for any finite number of rows and columns of $A$, without any large N approximations. In particular we treat the case when the Wishart-type random matrix contains redundant, non-random information, which is a new result. Th

Pierre van Baal

We attempt to deal with the orbifold singularities in the moduli space of flat connections for supersymmetric gauge theories on the torus. At these singularities the energy gap in the transverse fluctuations vanishes and the resulting breakdown of the adiabatic approximation is resolved by considering the full set of zero-momentum fields. These can not be de

N. Haba, T. Kondo, Y. Shimizu

We suggest a simple supersymmetric SO(10) grand unified theory in 6 dimensions which produces the suitable fermion mass hierarchies. The 5th and 6th dimensional coordinates are compactified on a $T^2/Z_2$ orbifold. The gauge and Higgs fields propagate in 6 dimensions while ordinal chiral matter fields are localized in 4 dimensions. The orbifolding and bounda

T. A. Lahde, D. O. Riska

The role of pion rescattering in $ππ$ decay of radially excited heavy quarkonia modeled in terms of a $Qππ$ coupling, is investigated within the framework of the covariant Blankenbecler-Sugar equation. The effects of pion rescattering (or pion exchange) are shown to be large, unless the coupling of the two-pion system to the heavy quarks is mediated by a fai

Iver Brevik, Andrei A. Bytsenko, Roger Sollie

The thermodynamic free energy F(β) is calculated for a gas consisting of the transverse oscillations of a piecewise uniform bosonic string. The string consists of 2N parts of equal length, of alternating type I and type II material, and is relativistic in the sense that the velocity of sound everywhere equals the velocity of light. The present paper is a con

G. E. Volovik

We discuss fermion zero modes within the 3+1 brain -- the domain wall between the two vacua in 4+1 spacetime. We do not assume relativistic invariance in 4+1 spacetime, or any special form of the 4+1 action. The only input is that the fermions in bulk are fully gapped and are described by nontrivial momentum-space topology. Then the 3+1 wall between such vac

Shin-ichi Fujimori, Akihiro Ino, Testuo Okane, Atsushi Fujimori

We report on the results of angle-resolved photoemission experiments on a quasi-one-dimensional $MX$-chain compound [Ni(chxn)$_2$Br]Br$_2$ (chxn = 1$R$,2$R$-cyclohexanediamine), a one-dimensional Heisenberg system with $S=1/2$ and $J \sim 3600$ K, which shows a gigantic non-linear optical effect. A "band" having about 500 meV energy dispersion is fou

Brett McInnes

Recent observations suggest that the cosmological equation-of-state parameter w is close to -1. To say this is to imply that w could be slightly less than -1, which leads to R.Caldwell's "Phantom cosmologies". These often have the property that they end in a "Big Smash", a final singularity in which the Universe is destroyed in a finite p

Ladislav Mista, Radim Filip, Jaromir Fiurasek

We investigate the separability, nonlocality and squeezing of continuous-variable analogue of the Werner state: a mixture of pure two-mode squeezed vacuum state with local thermal radiations. Utilizing this Werner state, coherent-state teleportation in Braunstein-Kimble setup is discussed.

Giuliano Benenti, Giulio Casati

We discuss the behavior of fidelity for a classically chaotic quantum system in the metallic regime. We show the existence of a critical value of the perturbation below which the exponential decay of fidelity is determined by the width of the Breit-Wigner distribution and above which the quantum decay follows the classical one which is ruled by the Lyapunov

Malakyan Yu. P

New phenomenon of temporal oscillations of nonlinear Faraday rotation in a driven four-level system is predicted. We show that in this system with one upper level, under the conditions of electromagnetically induced transparency created by a strong coupling field, the polarization rotation of weak probe light exhibits slowly damped oscillations with a freque

XuBo Zou, K. Pahlke, W. Mathis

We propose a scheme to implement quantum phase gate for two $Λ$ ions trapped in optical cavity. It is shown that quantum phase gate can be implemented by applying a laser addressing to a single ions in strongly detuned optical cavity. We further demonstrate that geometric quantum phase gate can be implemented by introducing a auxiliary ground state.

Chun-Hsien Wu, Chung-I Kuo, L. H. Ford

The retarded Van der Waals force between a polarizable particle and a perfectly conducting plate is re-examined. The expression for this force given by Casimir and Polder represents a mean force, but there are large fluctuations around this mean value on short time scales which are of the same order of magnitude as the mean force itself. However, these fluct

G. Kaniadakis

The one particle quantum mechanics is considered in the frame of a N-body classical kinetics in the phase space. Within this framework, the scenario of a subquantum structure for the quantum particle, emerges naturally, providing an ontological support to the orthodox quantum mechanics. This approach to quantum mechanics, constitutes a deductive and direct m

Spiridon Dumitru

The usual conjectures of quantum measurements approaches, inspired from the traditional interpretation of Heisenberg's ("uncertainty") relations, are proved as being incorrect. A group of reconsidered conjectures and a corresponding new approach are set forth. The quantum measurements, regarded experimentally as statistical samplings, are describ

Daniele Tommasini

I show that Quantum Electrodynamics (QED) predicts a sort of uncertainty principle on the number of the "soft photons" that can be produced in coincidence with the particles that are observed in any EPR experiment. This result is argued to be sufficient to remove the original EPR paradox. A signature of this soft-photons solution of the EPR paradox w

Jürgen Audretsch, Thomas Konrad, Artur Scherer

An experiment is proposed to visualize stroboscopically in real time the dynamics of a photon oscillating between two cavities. The visualization is implemented by a sequence of weak measurements (POVM), which are carried out by probing one of the cavities with a Rydberg atom and detecting a resulting phase shift by Ramsey interferometry. This way to measure

P. R. Silva

We propose an effective harmonic oscillator model in order to treat the fluctuations of the gravitational, strong and weak nuclear fields. With respect to the gravitational field, first we use the model to estimate its fluctuating strength, necessary to decohere the wavefunction of a cubic centimeter of air at the standard temperature and pressure conditions

M. Payami

Using the stabilized jellium model with self-compression, we have calculated the dissociation energies and the barrier heights for the binary fragmentation of charged silver clusters. At each step of calculations, we have used the relaxed-state sizes and energies of the clusters. The results for the doubly charged Ag clusters predict a critical size, at whic

A. Bertocchi, V. Bozzolan, G. Buceti, C. Centioli

After more than 10 years of activity, FTU (Frascati Tokamak Upgrade) has to face the problem of taking advantage of the new hardware and software technology saving all the investments yet done. So, for example, the 20 years old Westinghouse PLCs (communicating only through a serial line) have to be leaved in operation while a web-based tool has to be release

A. J. Sargeant, M. S. Hussein, M. P. Pato, N. Takigawa

The attenuation of the intraband intensity of a superdeformed band, which results from mixing with normally deformed configurations, is calculated using reaction theory. It is found that the sharp increase of the attenuation is mostly due to the tunnelling through a spin dependent barrier and not to the chaotic nature of the normally deformed states.

A. Ya. Berdnikov, Ya. A. Berdnikov, A. N. Ivanov, V. A. Ivanova

We follow Quark-gluon transport theory and analyse singularities of the ultra-relativistic and spherical expanding quark-gluon plasma. Within the linearized QCD oscillations and instabilities of the ultra-relativistic and spherical symmetric expanding quark-gluon plasma near global thermodynamical equilibrium are investigated in dependence on a chemical pote

N. Manojlovic, H. Samtleben

Schlesinger transformations are discrete monodromy preserving symmetry transformations of a meromorphic connection which shift by integers the eigenvalues of its residues. We study Schlesinger transformations for twisted sl_N-valued connections on the torus. A universal construction is presented which gives the elementary two-point transformations in terms o

F. M. Cucchietti, C. H. Lewenkopf, E. R. Mucciolo, H. M. Pastawski

We study the time evolution of two wave packets prepared at the same initial state, but evolving under slightly different Hamiltonians. For chaotic systems, we determine the circumstances that lead to an exponential decay with time of the wave packet overlap function. We show that for sufficiently weak perturbations, the exponential decay follows a Fermi gol

J. M. G. Gomez, R. A. Molina, A. Relano, J. Retamosa

The main signature of chaos in a quantum system is provided by spectral statistical analysis of the nearest neighbor spacing distribution and the spectral rigidity given by $Δ_3(L)$. It is shown that some standard unfolding procedures, like local unfolding and Gaussian broadening, lead to a spurious increase of the spectral rigidity that spoils the $Δ_3(L)$

E. Pelantová, A. M. Perelomov

We give the general solution of three Diophantine equations in the ring of integer of the algebraic number field ${\bf Q}[{\sqr 5}]$. These equations are related to the problem of determination of the minimum distance in quasicrystals with fivefold symmetry.

B. Z. Moroz, A. M. Perelomov

A problem posed in a remark by Pauli is discussed: is it possible to recover the state vector of a quantum system from the distribution functions of the physical observables of this system ?

F. Calogero, A. M. Perelomov

The eigenvalues of the 3 off-diagonal matrices of rank $n$ with elements $1+i cot[(j-k)π/n], sin^{-2}[(j-k)π/n]$ and $sin^{-4}[(j-k)π/n], (j=1,2,...,n, k=1,2,...,n, j\neq k)$ are computed. The sums over $k$ from 1 to $n-1$ of $cot(kπ/n) sin(2skπ/n)$ and $sin^{-p}(kπ/n) cos(2skπ/n)$ are moreover computed for $s$ integer and $p=2$ and 4. The results are given

David H. Brown

I present three models of plant--pathogen interactions. The models are stochastic and spatially explicit at the scale of individual plants. For each model, I use a version of pair approximation or moment closure along with a separation of timescales argument to determine the effects of spatial clustering on threshold structure. By computing the spatial struc

Robert Lauter, Bertrand Monthubert, Victor Nistor

We construct algebras of pseudodifferential operators on a continuous family groupoid G that are closed under holomorphic functional calculus, contain the algebra of all pseudodifferential operators of order 0 on G as a dense subalgebra, and reflect the smooth structure of the groupoid G, when G is smooth. As an application, we get a better understanding on

Osamu Fujino

The main purpose of this notes is to supplement the paper reid, which treated Minimal Model Program (also called Mori's Program) on toric varieties. We calculate lengths of negative extremal rays of toric varieties. As an application, we obtain a generalization of Fujita's conjecture for singular toric varieties. We also prove that every toric variet

Ruslan Sharipov

It is well known that Lagrangian dynamical systems naturally arise in describing wave front dynamics in the limit of short waves (which is called pseudoclassical limit or limit of geometrical optics). Wave fronts are the surfaces of constant phase, their points move along lines which are called rays. In non-homogeneous anisotropic media rays are not straight

Yoshihiro Takeuchi, Misako Yokoyama

For an orbifold M we define a homology group, called t-singular homology group t-H_q(M), which depends not only on the topological structure of the underlying space of M, but also on the orbifold structure of M. We prove that it is a b-homotopy invariant of orbifolds. If M is a manifold, t-H_q(M) coincides with the usual singular homology group. We calculate

R. Killip, A. Kiselev, Y. Last

We derive a general upper bound on the spreading rate of wavepackets in the framework of Schrödinger time evolution. Our result consists of showing that a portion of the wavepacket cannot escape outside a ball whose size grows dynamically in time, where the rate of this growth is determined by properties of the spectral measure and by spatial properties of s

Ronald Brown, Ilhan Icen

Previous work (Pradines, 1966, Aof and Brown, 1992) has given a setting for a holonomy Lie groupoid of a locally Lie groupoid. Here we develop analogous 2-dimensional notions starting from a locally Lie crossed module of groupoids. This involves replacing the Ehresmann notion of a local smooth coadmissible section of a groupoid by a local smooth coadmissible

R. Brown, I. Icen

We give a detailed description of the structure of the actor 2-crossed module related to the automorphisms of a crossed module of groupoids. This generalises work of Brown and Gilbert for the case of crossed modules of groups, and part of this is needed for work on 2-dimensional holonomy to be developed elsewhere (see math.DG/0009082).

V. Mathai, S. Yates

We study Harper operators and the closely related discrete magnetic Laplacians (DML) on a graph with a free action of a discrete group, as defined by Sunada. A main result in this paper is that the spectral density function of DMLs associated to rational weight functions on graphs with a free action of an amenable discrete group, can be approximated by the a

Raphael Bousso, Lisa Randall

An AdS_4 brane embedded in AdS_5 exhibits the novel feature that a four-dimensional graviton is localized near the brane, but the majority of the infinite bulk away from the brane where the warp factor diverges does not see four-dimensional gravity. A naive application of the holographic principle from the point of view of the four-dimensional observer would

Andrei Khrennikov

We study the role of context, complex of physical conditions, in quantum as well as classical experiments. It is shown that by taking into account contextual dependence of experimental probabilities we can derive the quantum rule for the addition of probabilities of alternatives. Thus we obtain quantum interference without applying to wave or Hilbert space a

S. Bellucci, A. Galajinsky, E. Ivanov, S. Krivonos

We study quantum mechanics of a massive superparticle in d=4 which preserves 1/4 of the target space supersymmetry with eight supercharges, and so corresponds to the partial breaking N=8 down to N=2. Its worldline action contains a Wess-Zumino term, explicitly breaks d=4 Lorentz symmetry and exhibits one complex fermionic kappa-symmetry. We perform the Hamil

K. Behrndt, E. Bergshoeff, D. Roest, P. Sundell

We study compactifications of string theory and M-theory to six dimensions with background fluxes. The nonzero fluxes lead to additional mass parameters. We derive the S- and T-duality rules for the corresponding (massive) supergravity theories. Specifically, we investigate the massive T-duality between Type IIA superstring theory compactified on K3 with bac

Biswajit Chakraborty

We show that the system where $CP^1$ model coupled to Hopf term can reveal fractional spin in a collective coordinate quantization scheme, provided one makes a transition to physically inequivalent sector within a same solitonic sector characterized by a nonvanishing topological number

Ali Mostafazadeh

We construct a realization of the algebra of the Z_3-graded topological symmetry of type (1,1,1) in terms of a pair of operators D_1: H_1 -> H_2, and D_2: H_2 -> H_3 satisfying [D_1D_1^\dagger,D_2^\dagger D_2]=0. We show that the sequence of the restriction of these operators to the zero-energy subspace forms a complex and establish the equality of the corre

S. G. Kamath

Following Dahl's method an exact Runge-Lenz vector M with two components M and M is obtained as a constant of motion for a two particle-system with charges e and e whose electromagnetic interaction is based on Chern-Simons electrodynamics. The Poisson bracket {M, M} = L but is modified by the appearance of the product e e as central charges.

I. Brevik, A. A. Bytsenko, B. M. Pimentel

The Casimir energy for the transverse oscillations of a piecewise uniform closed string is calculated. The great adaptability of this string model with respect to various regularization methods is pointed out. We survey several regularization methods: the cutoff method, the complex contour integration method, and the zeta-function method. The most powerful m

Alexander Kovner, Urs Achim Wiedemann

We consider the perturbative description of saturation based on the nonlinear QCD evolution equation of Balitsky and Kovchegov (BK). Although the nonlinear corrections lead to saturation of the scattering amplitude locally in impact parameter space, we show that they do not unitarize the total cross section. The total cross section for the scattering of a st

T. S. Biro, P. Levai, J. Zimanyi

We utilize the ALCOR model for mid-rapidity hadron number predictions at AGS, SPS and RHIC energies. We present simple fits for the energy dependence of stopping and quark production.

I. I. Tkachev

Inflationary cosmology is reviewed. Particular attention is given to processes of creation.

M. Ciuchini

An updated determination of the parameters of the Cabibbo-Kobayashi-Maskawa matrix is presented.

Fabio Zwirner

The present experimental and theoretical knowledge of the physics of electroweak symmetry breaking is reviewed. Data still favor a light Higgs boson, of a kind that can be comfortably accommodated in the Standard Model or in its Minimal Supersymmetric extension, but exhibit a non-trivial structure that leaves some open questions. The available experimental i

Thomas Becher, Stephan Braig, Alex Kagan, Matthias Neubert

Implications of a 2 - 5.5 GeV sbottom and 12 - 16 GeV gluino masses for rare B decay phenomenology are discussed. An effective Hamiltonian is constructed in which the gluinos are integrated out and a \tilde{b} squark remains among the light flavor degrees of freedom. Restrictive constraints come from $b \to s γand b \to sg, but they allow a substantially enh

Ji-sheng Chen, Jia-rong Li, Peng-fei Zhuang

Based on the kinetic theory, the non-Abelian medium property of hot Quark-Gluon Plasma is investigated. The nonlinearity of the plasma comes from two aspects: The nonlinear wave-wave interaction and self-interaction of color field. The non-Abelian color permittivity is obtained by expanding the kinetic equations to third order. As an application, the nonline

Gabriella Pasztor, Thomas G. Rizzo

In this report we summarize the work performed at Snowmass 2001 on the physics of extra dimensions. We divide these analyses into the following classes: searches for extra dimensional phenomena, identification of specific new physics scenarios, studies of black hole production and non-commutative QED.

Vladimir K. Petrov

Coupling dependence on lattice spacing and size is estimated analytically at β-> \infty region where for a->0 the critical area is shifted in accordance with Callan-Symanzik relation. In considered approximation no trace of critical behavior is found in this area.

SCALAR Collaboration, S. Muroya, A. Nakamura, C. Nonaka

Using lattice QCD with dynamical Wilson fermions, we study I=0 and $J^{P}=0^{+}$ channel which is constructed by $\frac{1}{\sqrt{2}}(\bar{u}u+\bar{d}d)|0>$, in order to search for the $σ$ meson. Our preliminary result shows that the connected and disconnected diagrams contribute to the $σ$ meson propagator in the same order.

E. Kajfasz

We briefly describe the production, installation and commissioning of the new 800,000 channel D0 Silicon Microstrip Tracker to be used for the 2 fb$^{-1}$ of the Run IIa at the Tevatron.

S. Prell

We report the observation of CP violation in the $B^0$ meson system. Using a novel technique for time-dependent measurements, we measure a non-zero value for the CP-violating amplitude $\sin 2β$ at the 4.1 $σ$ level. We also report on precision measurements of the $B^+$ and $B^0$ lifetimes and the $B^0\bar{B}^0$ mixing frequency $Δm_d$ obtained with the same

Patrick J. Sutton, Lee Samuel Finn

By comparing the observed orbital decay of the binary pulsars PSRB1913+16 and PSRB1534+12 to that predicted by general relativity due to gravitational-wave emission, we are able to bound the mass of the graviton to be less than $7.6\times10^{-20} \text{eV}/c^2$ at 90% confidence. This is the first such bound to be derived from dynamic gravitational fields. I

A. R. Prasanna

In this we briefly cover the covariant approach to describe inertial forces in general relativity and in particular look at the behaviour of the cumulative drag index for stationary Kerr geometry.

Kyriakos N. Sgarbas, Nikos D. Fakotakis, George K. Kokkinakis

In this paper we present a lexicon-based approach to the problem of morphological processing. Full-form words, lemmas and grammatical tags are interconnected in a DAWG. Thus, the process of analysis/synthesis is reduced to a search in the graph, which is very fast and can be performed even if several pieces of information are missing from the input. The cont

P. Sichta, J. Dong, G. Oliaro, P. Roney

The National Spherical Torus Experiment (NSTX) is an innovative magnetic fusion device that was constructed by the Princeton Plasma Physics Laboratory (PPPL) in collaboration with the Oak Ridge National Laboratory, Columbia University, and the University of Washington at Seattle. Since achieving first plasma in 1999, the device has been used for fusion resea

Wei Cheng, Shang-Fen Ren

Raman intensities of Si quantum dots (QDs) with up to 11,489 atoms (about 7.6 nm in diameter) for different scattering configurations are calculated. First, phonon modes in these QDs, including all vibration frequencies and vibration amplitudes, are calculated directly from the lattice dynamic matrix by using a microscopic valence force field model combined

Weinan E, Zhongyi Huang

We present a coupled atomistic-continuum method for the modeling of defects and interface dynamics of crystalline materials. The method uses atomistic models such as molecular dynamics near defects and interfaces, and continuum models away from defects and interfaces. We propose a new class of matching conditions between the atomistic and continuum regions.

I. Kh. Zharekeshev, B. Kramer

Using the Anderson model for disordered systems the fluctuations in electron spectra near the metal--insulator transition were numerically calculated for lattices of sizes up to 28 x 28 x 28 sites. The results show a finite--size scaling of both the level spacing distribution and the variance of number of states in a given energy interval, that allows to loc

E. Babic, Dj. Miljanic, K. Zadro, I. Kusevic

m-H loops for virgin and neutron irradiated bulk and powder samples of MgB_{2} were measured in the temperature range 5-30 K in magnetic field B<= 1 T. The irradiation at thermal neutron fluences 9*10^{13} and 4.5*10^{14} cm^{-2} caused very small enhancement of m-H loops at lower temperatures (T<20 K), whereas the effect at high temperatures was unclear due

J. Dorignac, S. Flach

We analyze the quantum properties of a system consisting of two nonlinearly coupled pendula. This non-integrable system exhibits two different symmetries: a permutational symmetry (permutation of the pendula) and another one related to the reversal of the total momentum of the system. Each of these symmetries is responsible for the existence of two kinds of

A. Halbritter, Sz. Csonka, O. Yu. Kolesnychenko, G. Mihaly

Dynamic evolution of the connective neck in Al and Pb mechanically controllable break junctions was studied during continuous approach of electrodes at bias voltages V_b up to a few hundred mV. A high level of power dissipation (10^-4 - 10^-3 W) and high current density (j > 10^10 A/cm^2) in the constriction lead to overheating of the contact area, electromi

Mona Berciu, R. N. Bhatt

We show that the choice of the sign of the hopping matrix in our impurity band model for disordered III-V diluted magnetic semiconductors [PRL 87, 107293 (2000); cond-mat/0111045] is justified: with this choice, the impurity band is placed inside the gap and it has a mobility edge, as expected for a disordered system. The other sign choice, suggested in cond

Jean Bragard, Alain Karma, Youngyih H. Lee, Mathis Plapp

Even though our theoretical understanding of dendritic solidification is relatively well developed, our current ability to model this process quantitatively remains extremely limited. This is due to the fact that the morphological development of dendrites depends sensitively on the degree of anisotropy of capillary and/or kinetic properties of the solid-liqu

T. M. Gassym, H. A. Hasanov

The transverse Nernst--Ettingshausen effect and thermopower of hot charge carriers in nondegenerate impure semiconductors placed at high electric and nonquantized magnetic fields in the nondiffusion approximation is studied. Arbitrary heating and mutual drag of electrons and long wavelength phonons interacting with electrons are considered. The spectrum of e

Anna Painelli, Luca Del Freo, Zoltan G. Soos

The complex interplay among on-site energy, Hubbard U, and coupling to Holstein and Peierls phonons at the neutral-ionic phase transition is discussed using diagrammatic valence bond calculations. The charge transfer and dimerization amplitudes and the infrared intensity of molecular vibrations are studied in the transition region.

Kevin P. Duncan, Balazs L. Gyorffy

We have developed a semiclassical approach to solving the Bogoliubov - de Gennes equations for superconductors. It is based on the study of classical orbits governed by an effective Hamiltonian corresponding to the quasiparticles in the superconducting state and includes an account of the Bohr-Sommerfeld quantisation rule, the Maslov index, torus quantisatio

M. Hennion, F. Moussa, F. Wang, J. Rodríguez-Carvajal

The ferromagnetic and insulating state observed in La$_{1-x}$Ca$_{x}$MnO$_3$, 0.125$<$x$<$0.2, is characterized by structural and magnetic anomalies below T$_C$, similar to those observed in the x$_{Sr}$$\approx$1/8. A neutron scattering study of the superlattice {\bf Q$_0$}= (0,0,1+/4)$_{cub}$ peak, and of the magnetic excitations are reported in the x$_{Ca

A. S. Kovalev, S. Komineas, F. G. Mertens

Vortex-antivortex pairs in 2D easy-plane ferromagnets have characteristics of solitons in two dimensions. We investigate numerically and analytically the dynamics of such vortex pairs. In particular we simulate numerically the head-on collision of two pairs with different velocities for a wide range of the total linear momentum of the system. If the momentum

Eduardo R. Mucciolo, Claudio Chamon, Charles M. Marcus

We propose a mechanism by which an open quantum dot driven by two ac (radio frequency) gate voltages in the presence of a moderate in-plane magnetic field generates a spin polarized, phase coherent dc current. The idea combines adiabatic, non-quantized (but coherent) pumping through periodically modulated external parameters and the strong fluctuations of th

Lutz Brusch, Heiko Kuehne, Uwe Thiele, Markus Baer

We study a model for a thin liquid film dewetting from a periodic heterogeneous substrate (template). The amplitude and periodicity of a striped template heterogeneity necessary to obtain a stable periodic stripe pattern, i.e. pinning, are computed. This requires a stabilization of the longitudinal and transversal modes driving the typical coarsening dynamic

J. Reijniers, A. Matulis, K. Chang, F. M. Peeters

We show how snake-orbit states which run along a magnetic edge can be confined electrically. We consider a two-dimensional electron gas (2DEG) confined into a quantum wire, subjected to a strong perpendicular and steplike magnetic field $B/-B$. Close to this magnetic step new, spatially confined bound states arise as a result of the lateral confinement and t

M. Kenzelmann, R. A. Cowley, W. J. L. Buyers, Z. Tun

We report inelastic time-of-flight and triple-axis neutron scattering measurements of the excitation spectrum of the coupled antiferromagnetic spin-1 Heisenberg chain system CsNiCl3. Measurements over a wide range of wave-vector transfers along the chain confirm that above T_N CsNiCl3 is in a quantum-disordered phase with an energy gap in the excitation spec

M. S. Oey

This review presents a perspective on recent advances in understanding neutral ISM structure in external galaxies. HI is a fundamental probe of galactic baryonic material, and its structure and distribution offer vital signatures of dynamical and evolutionary processes that drive star formation and galaxy evolution. New, high-resolution HI data cubes for ext

C. Solorzano-Inarrea, C. Tadhunter, J. Bland-Hawthorn

We present deep, narrow-band and continuum images of the powerful z=0.811 radio galaxy 3C265, taken with the TTF on the WHT, together with detailed long-slit spectroscopic observations along the axis defined by the UV/optical emission elongation. The deep images reveal the existence of cones in the ionization structure within ~7 arcsec (58 kpc) of the nucleu

Antonio C. C. Guimarães

Weak gravitational lensing is a promising tool for the study of the mass distribution in the Universe. Here we report some partial results that show how lensing maps can be used to differentiate between cosmological models. We pay special attention to the role of noise and smoothing. As an application, we use mock convergence fields constructed from N-body s

G. J. Madsen, L. M. Haffner, R. J. Reynolds

The Wisconsin H-Alpha Mapper (WHAM) has completed a one-degree resolution, velocity-resolved northern sky survey of H-alpha emission from our Galaxy. The unprecedented sensitivity of the instrument and accurate spectral subtraction of atmospheric features allow us to detect Galactic features as faint as 0.1 Rayleighs (EM ~ 0.25 cm^{-6} pc). This survey allow

Marek Sikora, Greg Madejski

This paper reviews the topic of sub-parsec - scale jets in quasars, and covers the the following issues: observations of parsec and sub-parsec scale jets; energy dissipation and particle acceleration; radiative processes; magnetic fields, pair content, and energetics; and variability and its relation to the central engine activity. In particular, we describe

M. Jura, C. Chen, P. Plavchan

We have obtained 11.7 and 17.9 micron images at the Keck I telescope of the circumstellar dust emission from L2 Pup, one of the nearest (D = 61 pc) mass-losing, pulsating, red giants that has a substantial infrared excess. We propose that the wind may be driven by the stellar pulsations with radiation pressure on dust being relatively unimportant, as describ

Kyu-Hyun Chae

Fourier series solutions to the deflection and magnification by a family of three-dimensional cusped two power-law ellipsoidal mass distributions are presented. The cusped two power-law ellipsoidal mass distributions are characterized by inner and outer power-law radial indices and a break (or, transition) radius. The model family includes mass models mimick

Jaime Alvarez-Muñiz, Ralph Engel, Todor Stanev

Recently the AGASA Collaboration presented data suggesting a significant clustering of ultra-high energy cosmic rays coming from the outer Galaxy region. In this paper we calculate expected cosmic ray arrival distributions for several simple, limiting source location scenarios and investigate the possibility of clustering and correlation effects. The role of

Karsten Jedamzik

This article gives a brief qualitative description of the possible evolution of the early Universe between the end of an inflationary epoch and the end of Big Bang nucleosynthesis. After a general introduction, establishing the minimum requirements cosmologists impose on this cosmic evolutionary phase, namely, successful baryogenesis, the production of cosmi

I. Burud, F. Courbin, P. Magain, C. Lidman

We present optical V and i-band light curves of the gravitationally lensed BAL quasar HE2149-2745. The data, obtained with the 1.5m Danish Telescope (ESO-La Silla) between October 1998 and December 2000, are the first from a long-term project aimed at monitoring selected lensed quasars in the Southern Hemisphere. A time delay of 103+/-12 days is determined f

D. Garcia-Alvarez, D. Jevremovic, J. G. Doyle, C. J. Butler

Spectroscopic observations covering the wavelength range 3600--4600Åare presented for a large flare on the late type M dwarf AT Mic (dM4.5e). A procedure to estimate the physical parameters of the flaring plasma has been used which assumes a simplified slab model of the flare based on a comparison of observed and computed Balmer decrements. With this procedu

Anthony Minter, Felix J. Lockman

HI 21 cm observations with the NRAO 140 Foot telescope have revealed a giant HI cloud (G28.17+0.05) in the Galactic plane that has unusual properties. The cloud is 150 pc in diameter, is at a distance of 5 kpc, and contains as much as 100,000 Solar Masses of atomic hydrogen. The cloud consists of a cold core, T~10 K, and a hotter outer envelope, T < 200 K. T

A. H. Minter

In this paper I investigate what factors -- both observational and physical -- can change the measured slope of the observed 21cm HI power spectrum. The following effects can make the observed turbulence appear two dimensional rather than three dimensional: 1) if the turbulence is contained in a thin filament or slab; 2) if the medium has a high optical dept

M. Douspis, A. Blanchard, R. Sadat, J. G. Bartlett

We present the results of a combined analysis of cosmic microwave background (CMB) and X-ray galaxy clusters baryon fraction to deduce constraints over 6 in flationnary cosmological parameters. Such a combination is necessary for breaki ng degeneracies inherent to the CMB.

Maurice H. P. M. van Putten

The spin-energy $E_{rot}$ of a Kerr black hole surrounded by a torus may power emissions in multiple windows. The recently determined true GRB-energy of $3-5\times 10^{50}$ erg indicates a minor fraction $E_j/E_{rot}\simeq 0.1%$ in baryon poor ouput, here considered as jets along open magnetic flux-tubes from the horizon to infinity. A major fraction $E_{gw}

David Shapakidze, George Machabeli, George Melikidze, David Khechinashvili

We examine linear and quasi-liner stages of Cherenkov-drift instability in the relativistic magnetized electron-positron plasma. The external magnetic field lines are assumed to be slightly curved. In this case the curvature drift of relativistic beam particles plays decisive role in the development of the instability. Quasi-linear relaxation of the relativi